I guess that I have read (and used) too much XP driven programming and testing, so I started devising tests after each sysadmin change also. So, here are some tips assorted by services:

smtp

Test all MX records for domain bobcatsss2008.org by sending e-mail to test@bobcatsss2008.org

host -t mx bobcatsss2008.org | awk '{ print $4 }' | xargs -i swaks  -t test@bobcatsss2008.org -s {}